In different fields of application, for example vacuum technology, the processing of food products or productronics, it is impossible or undesirable to lubricate rolling bearings with grease or oil, or the operating temperature is higher than the heat resistance of the lubricant. There is therefore a need for special rolling bearings which have a high temperature resistance and media resistance while simultaneously having optimum rolling bearing properties and also being suitable for a dry run. Since a lubricant in grease or oil form is dispensed with and owing to the high temperature resistance, these rolling bearings are highly suited to use in food technology installations and in bearing points subjected to high temperatures, for example in an internal combustion engine or the like.
Suitable, known rolling bearings such as these frequently have ceramic rolling elements which, however, bear a high risk of fracture when subjected to repeated, pulse-like stresses. The production of these rolling elements is also expensive and often not economically justifiable. In addition, needle rollers cannot be produced from ceramic materials, and therefore ball bearings with ceramic balls are primarily available.
However, it is also known to equip rolling bearings with a graphite cage in which the rolling elements are held. Graphite itself is suitable as a lubricant; i.e. as a result of the minimal abrasion of graphite from the cage, a rolling bearing of this type has self-lubrication and can therefore be used in the critical fields of use mentioned. However, to date, a drawback is that graphite cages such as these had to be produced in a complex manner with material removal by turning or milling. This production process is complicated, as has already been indicated in DE 36 11 907. This is because a graphite component of this type has a high susceptibility to fracture, and this is problematic during production. Therefore, the production of graphite cages produced with material removal is carried out only on a small scale and is very expensive. Nevertheless, highly effective rolling bearings with minimal self-lubrication can be assembled using such a graphite cage, and these rolling bearings are outstandingly suitable for dry running applications and other applications with minimum amounts of lubrication or media lubrication applications.